Recent statistics suggest that the world-wide progress to reduce impaired driving may have come to an end. In addition, alcohol control policies in North America have been moving towards greater liberalization, despite evidence that increased availability is related to increased consumption and health- and safety-related problems. One control policy for which there is very little research information is hours of sale. On May 1, 1996, the Ontario government amended the Liguor Licence Act to extend the hours of alcohol sales and service in licensed establishments from 1 to 2 am. This introduction of the extended drinking hours provides an excellent natural experiment to evaluate an important alcohol control policy. The purpose of this study is to evaluate the health and safety impact of this amendment in Ontario, Canada. Three competing hypotheses will be tested: 1) the alcohol availability hypothesis; 2) the "power drinking" hypothesis, and 3) the temporal shift in drinking hypothesis. This study will use a multi-methods, multiple-measures approach within a quasi- experimental multiple comparison time series design. The criterion datasets are monthly alcohol-related fatalities and injuries for Ontario, total and for the 11-12pm, 12-1am, 1-2am and 2-3am time windows, for 3 years pre- and 2 years post-policy change, compared to the neighbouring regions of Manitoba, New York and Michigan. Additional measures are alcohol-related trauma cases, and retail and licensee total alcohol sales data for the same time periods. Qualitative information pertaining to licensed establishments will serve to enhance and clarify the results of the quantitative analyses. In addition, the study will examine the effects of the policy change on Windsor, Ontario and Detroit, Michigan to determine whether Windsor's extended drinking hours to match Detroit's 2am bar closing has reduced the cross-border drinking of Ontario residents. Alcohol-related casualties for both cities will be subjected to time-series analyses. In addition, Detroit data will be disaggregated to analyze the trends of alcohol-related casualties involving Ontario drivers.